run lox tests from the book's repo, inspired by @hparker

FossilOrigin-Name: f477507f650934b9117cce181e4cdc50dda31c1126651319132feb7c768a1a93

ruby/test/test_helper.rb

@@ -2,5 +2,37 @@ require "minitest"
 
 module Lox
   class Test < Minitest::Test
+    LOX_BIN = File.expand_path("../bin/lox", __dir__)
+
+    def assert_lox(path)
+      src = File.read(path)
+
+      expected_out = src.scan(/(?<=\/\/ expect: )(?~\n)/).join("\n")
+
+      out, _err, _status = Open3.capture3(LOX_BIN, path)
+
+      assert_equal expected_out, out
+    end
+  end
+
+  book_src = File.expand_path(ENV.fetch("CRAFTING_INTERPRETERS_SRC"))
+  Dir.chdir(book_src) do
+    lox_tests = Dir["./test/**/*.lox"]
+      .group_by {|path| path.rpartition(?/).first.sub(/\.\/test\/?/, "") }
+
+    lox_tests.each do |dir, paths|
+      klass = Class.new(Test) do
+        paths.each do |path|
+          name = File.basename(path, ".lox")
+          define_method("test_#{name}") do
+            assert_lox File.expand_path(path, book_src)
+          end
+        end
+      end
+
+      suite = dir.split(?/).map(&:capitalize).join
+      suite = "Root" if suite.empty?
+      Object.const_set("Test#{suite}", klass)
+    end
   end
 end

ruby/test/test_lox.rb

@@ -34,4 +34,3 @@ class TestRunner < Lox::Test
     runner.run("src")
   end
 end
-